Masked gunmen kidnapped two Americans and a Briton from their Baghdad residence Thursday in an attack that appeared to herald a new level of danger for foreign civilians in Iraq.

The abduction of the three private contractors, which occurred in one of the capital's most affluent neighborhoods, was the latest in a string of kidnappings by insurgents seeking to evict U.S. military forces and topple Iraq's interim government. In an assault similar to the kidnapping of two Italian aid workers from their offices last week, as many as 10 gunmen in a minivan pulled up in front of the contractors' two-story house, barged inside the gated compound and snatched the three Westerners without firing a shot, according to neighbors.

The U.S. Embassy in Baghdad identified the two American contractors as Jack Hensley and Eugene "Jack" Armstrong but did not provide their ages or home towns. The British Foreign Office did not identify the captured Briton. All three worked for Gulf Supplies and Commercial Services, a private contractor based in the United Arab Emirates that is working on reconstruction projects in Iraq, said Khaled Abbas, a company spokesman.

No group asserted immediate responsibility for the kidnapping, but the U.S.-led military command in Baghdad said its forces launched airstrikes on two facilities used by members of an insurgent organization led by Abu Musab Zarqawi, the Jordanian-born militant believed to be responsible for numerous kidnappings, car bombings and other attacks.

The first strike targeted a house in the restive city of Fallujah, 35 miles west of Baghdad, where Zarqawi followers had stashed weapons, the military said.

The second, larger strike was aimed at a "terrorist meeting site" southwest of Fallujah and killed 60 non-Iraqi fighters who had gathered "to plan attacks against the Iraqi people, Iraqi security forces and multinational forces," the military said in a statement. Approximately 90 foreign fighters had assembled at the site, a compound surrounded by fields near the town of Qaryat Rufush, the military said.

The 9:45 p.m. airstrike destroyed three buildings, the military said in the statement. When survivors fled into the town, "multinational forces discontinued the engagement of those terrorists in order to protect the civilian populace and minimize collateral damage to the town," the military said.

The attack appeared to be one of the largest and most successful efforts to target foreign fighters who have been drawn to Fallujah, a city that, until April, was patrolled by U.S. Marines but now is firmly in the control of insurgents. U.S. military officials say they believe the foreign fighters have been using Fallujah as a base to stage attacks in Baghdad.

Although U.S. ground forces remain on the city's fringe, warplanes have been striking targets in Fallujah associated with Zarqawi's network during the past two weeks in an attempt to weaken the group's hold over the city. The strikes have been directed at safe houses and weapons caches, but few have killed major concentrations of fighters, who eschew gathering in large groups to avoid detection by reconnaissance aircraft.

There was no independent confirmation of the deaths from Thursday's airstrike and no immediate reports from the scene. The attack on the weapons cache in Fallujah was conducted, the military said in a statement, after "sources reported the presence of terrorists, foreign fighters, and weapons systems that were intended for use" against Iraqi and U.S.-led forces.

In Ramadi, a city west of Fallujah that also has been racked by insurgent violence, U.S. Marines and soldiers launched an offensive against a little-known group with ties to Zarqawi's organization, the military said. The offensive, dubbed Operation Hurricane, "was designed to discover and remove illegal weapons and ammunition caches and to disrupt the Daham terrorist network," the military said.

The U.S. Marine command, which is responsible for Fallujah, Ramadi and the rest of Iraq's vast western province of Anbar, reported that three Marines were killed Thursday. The command also reported Thursday that a fourth Marine died of wounds sustained Wednesday. The Marines did not provide details of where or how the four were killed, citing operational security concerns.

The Associated Press reported that Iraqi police found the corpse of a man they believe to be a foreigner north of Baghdad. The body, which had blond hair and Western features, was pulled from the Tigris River near the village of Yethrib, Capt. Hakim Azawi, head of security at the teaching hospital in the city of Tikrit, told the AP. The man, who was described as tall, was shot in the back of the head, according to the AP.

In Baghdad's Mansour district, where the three contractors were kidnapped, neighbors said as many as 10 gunmen pulled up to the house shortly after dawn as one of the occupants opened the large metal gate to the driveway to turn on a generator in front of the compound. Several armed men, their faces shrouded in red-and-white scarves, forced their way in, the neighbors said. Within a few minutes, the three Westerners were forced into their own Nissan sedan and driven away by the captors, the neighbors said.

One of the neighbors, who identified herself as Um Ibrahim, said she heard the kidnappers tell the contractors to "walk quickly" and then to "get in the car."

Another neighbor, Ziyad Tariq, said he saw one of the captors dragging a hostage by the collar and pushing him into a car parked outside the house.

Tariq said that the contractors had two guards but that neither was on duty at the time of the kidnapping. Abbas, the company spokesman, said the house was supposed to be protected by armed guards 24 hours a day.

The contractors had tried to blend into the upscale neighborhood of large, walled-off homes. There were no concrete barriers or other indications that Westerners were living inside. Neighbors described the contractors as polite, discreet men who had lived there for eight months.

"They came to help the Iraqis," Ibrahim said. "Why do they want to hurt them? This is not fair."

Thursday's incident, like the kidnapping of the Italian aid workers, suggested that foreigners' attempts to blend into the community by not having conspicuous armed guards and other security measures have not fooled insurgents. The Italians, both women, were captured with two Iraqi employees inside their office, which was not guarded.

Other foreigners believed to be in the hands of insurgents include two French journalists and an Iraqi American businessman.

Special correspondent Bassam Sebti contributed to this report.

U.S. soldiers stand in front of the Baghdad house where three foreign contractors were captured by insurgents.